This invention relates to centrifuge systems for the general processing of fluids and, more specifically, a centrifugal device for liquids, such as blood.
A system, that permits connecting a rotating unit with a flexible tube or a cord, forming an open loop of which one extremity is integral during rotation with the axis of the rotating unit at a speed 2xcfx89 while the other extremity, coaxially located with respect to the first, is stationary and that the open loop is driven at a speed xcfx89, causing a rotation of the flexible tube around its own axis at a speed xe2x88x92xcfx89, thus eliminating any twisting of this flexible tube, is revealed in U.S. Pat. No. 3,586,413. This principle that permits eliminating any joint between the flexible tube and the rotating unit has been largely applied in a large number of centrifugal devices. Taking into account the speed of the rotating unit in a centrifuge, the flexible tube rotating on itself at the xe2x88x92xcfx89 speed is subject to a traction effort caused by the centrifugal force, to a bending stress caused by the rotation on itself of the portion of the tube forming the open loop at the xe2x88x92xcfx89 speed, as well as a temperature increase caused by the work of the viscous forces in the substance due to the aforementioned bending. However, in the case of centrifuging blood, the temperature rise must be  less than 5xc2x0 C.
Taking into account these various stresses has led to solutions that, use centrifugal units of a relatively flat form and of a diameter considerably higher than 200 mm, with the xcfx89 rotating speed generally situated around 200 rad/sec, with the latter in some cases going up to 400 rad/sec. This choice permits limiting the rotating speed, reducing the bending and traction stress on the flexible tube while obtaining an acceptable flow rate for the liquid. This choice, which has largely spread in the field of centrifuges for blood, obviously leads to a centrifugal rotor of a relatively large diameter. Such a centrifugal rotor, taking into account the centrifugal forces to which it is subjected and its large diameter, must be sized to withstand these efforts, resulting in a rotor that weighs several kilos, so that it no longer is economical to produce a rotor of this type in disposable form, like in the case of plasmapheresis for the purpose of collecting plasma.
As such, in U.S. Pat. No. 4,076,169, a disposable enclosure has been proposed for centrifuging a liquid that contains suspended particles such as blood. Since such a disposable enclosure would not withstand the centrifugal efforts, it is installed in a housing located inside a rotor consisting of two circular half-shells fitting into each other. Installation of the centrifugal enclosure in the rotor housing requires a disassembly and an assembly operation of the rotor, its opening and the installation of the centrifugal enclosure.
A solution of the same type is described in U.S. Pat. No. 4,010,894, in U.S. Pat. No. 4,834,890, in U.S. Pat. No. 4,934,995 as well as in U.S. Pat. No. 4,531,932. In all these separation devices, the disposable separation enclosure consists of a flexible bag located in a support rotor, involving handling that is considerably less easy than with a rigid component.
In other solutions, like the one described in U.S. Pat. No. 4,108,353, centrifugal enclosures are positioned on the rotor presenting positioning and securing components for these enclosures. Again, in this case, installation of these enclosures requires a certain number of movements that are delicate and time-consuming. Moreover, such a system requires the presence of several enclosures, even in number, for the centrifugal rotor to be balanced. Such a system is consequently not practical for centrifugation in line with taking blood.
The only rigid rotors proposed in the case of separating blood components through centrifuging are those described in U.S. Pat. No. 4,330,080, in U.S. Pat. No. 4,540,397 as well as in U.S. Pat. No. 5,350,514. Besides a separation enclosure in the form of a disk of more than 200 mm in diameter, the rotor includes a tubular body on which two ring-shaped guiding surfaces are arranged and, between them, a toothed ring to engage in a drive pinion.
Mounting and dismounting of this rotor requires removing one of the three guide rollers engaged with each of the ring-shaped surfaces of the rotor. Since during centrifugation these removable rollers must ensure retention of the rotor, locking devices for these rollers must be provided for. Replacing these disposable rotors represents a complex operation that must be done carefully, taking into account the danger that might represent the accidental separation of the rotor during centrifugation.
In addition to these problems, the dimensions and designs of these rotors result in heavy devices that are large and expensive and that are unfit for plasmapheresis in line with taking blood. If, in a therapeutic application, the price of a disposable rotor does not have a determining importance, this price is determining. But if the blood cells, such as erythrocytes that take a long time for the human body to produce could to be reinjected into the donor, and the latter could give blood more frequently. However, this can only be done at the same time that blood is being taken and, for that, separation enclosures are required that can be produced at a sufficiently low price and that can be exchanged easily and reliably.
The purpose of this invention is to remedy, at least partially, the abovementioned inconveniences.
In a first embodiment of the invention, there is provided a centrifugal device for liquids containing suspended particles, such as blood. The centrifugal device includes a centrifugal unit with a center and a rotation axis. A plurality of channels connects the center of the centrifugal unit to a peripheral separation chamber, each channel having a central extremity. A plurality of tubes have first and second extremities, with the central extremities of the respective channels attached to the first extremities of the tubes and the second extremities of the tubes being angularly stationary and coaxially located with respect to the rotating axis. First drive units turn the tubes around said rotating axis at an angular speed xcfx89. Second drive units turn the centrifugal unit around said rotating axis at an angular speed 2xcfx89. The centrifugal unit has a radius between 25 and 50 mm and a height between 75 and 125% of the radius.
In accordance with related embodiments of the invention, the centrifugal unit may be capable of rotating at an angular speed 2xcfx89 greater than 500 rad/sec. Liquid introduced to the centrifugal unit may be capable of flowing at a rate of less than 100 mL/min. The tubes may be capable of withstanding a traction force of  less than 0.7 N/mm2, have an elasticity module of  less than 5 N/mm2, and have a rupture strength at alternate bending of higher than 1.5 N/mm2. The centrifugal device may have the form of a bowl that includes a bottom part attached to a top part so as to form said separation chamber. The tubes may form open loops around the centrifugal unit and may be incorporated in one flexible tubular component. The diameter of a cross-section of the tubular component may not exceed 7 mm.
In accordance with further related embodiments of the invention, use of the device may include putting said liquid to be centrifuged under pressure (P) to produce a flow at a given rate. The degree of purity is measured for at least one of the centrifuged components. The proportion of the respective flow rates is regulated for the two components coming from centrifugation according to said degree of purity.
In accordance with another embodiment of the invention, a centrifugal unit includes a centrifugal component and a plurality of tubes. The unit is capable of turning around an axis to separate components of a liquid, such as blood. The plurality of tubes are incorporated into a single tubular component. The unit includes a base in the form of a disk. An external cylindrical wall and an internal cylindrical wall extends from the base so as to define a ring-shaped separation chamber among each other. A tubular housing almost extending coaxially to the rotating axis from the base receives an end of a tubular unit. A plurality of channels extend radially in the base of the centrifugal unit, with each channel providing communication between a respective tube of the tubular unit and the separation chamber. The centrifugal unit has a radius between 25 and 50 mm and a height between 75 and 125% of the radius.
In accordance with another embodiment of the invention, there is provided a device to centrifuge a liquid containing suspended particles, such as blood. The device includes a first drive component mounted to pivot around an axis, A second drive component is mounted to pivot coaxially with respect to the pivoting axis of the first drive. Devices drive the first and second drive components at a 2:1 ratio. A centrifugal unit coupled but removable to the first drive component has a tubular housing coaxially connected to the pivoting axis. The centrifugal unit has a radius between 25 and 50 mm and a height between 75 and 125% of the radius. A tubular component is coupled at a first extremity to the tubular connection housing of the centrifugal unit, and at a second extremity to the connecting tubular housing, and defines an axis that is coaxially located to said pivoting axis. The tubular component is joined at the second drive component to rotate. The tubular component further incorporates a plurality of tubes installed inside, with each tube having an elliptic cross-section to facilitate the rotation of the tubular component around the longitudinal axis.
The centrifugal device according to this invention permits dividing the weight of the centrifugal unit by about 5 with respect to the known disposable rigid units. This weight reduction that also permits having a more compact centrifugal unit, permits reducing the weight of the centrifugal device, reducing its size, while facilitating its handling. As such, this device offers a new field of application for this type of device, since it facilitates its transportation by virtue of its reduction in terms of weight and size; besides the known applications in a hospital setting, it can be used in blood collection vehicles and permit the re-injection of the donor""s own erythrocytes.